State of the art microprocessors circuits are dramatically increasing in power consumption and power density as functional requirements continue to drive circuit complexity. Microprocessor power consumption is emerging as the greatest problem facing designers of computer systems. Not only does the electrical circuitry itself have to be designed for operation at high levels of power consumption and elevated temperature, but designers also have to address overall system level mechanisms for dissipating large amounts of heat. Increases in operating temperature cause increases in power consumption, which can result in further temperature increases, leading to further power consumption and so on, creating a self-reinforcing undesirable scenario. Elaborate cooling system designs, including the use of heat pipes as well as active refrigeration based cooling systems, are routinely employed to maintain logic circuitry within desired operating temperature ranges. As a result, very high power bills are often associated with the operation of computers and the cooling systems they require. The requirement for microprocessor power dissipation increases the cost of cooling and packaging design, reduces system reliability, complicates power supply circuitry design, and reduces battery lifetime. Power consumption and the need for cooling often also impact geographical location decisions for deployment of large computer complexes.
Computer circuits can be viewed as entropy machines. Although computer circuits consume large amounts of power, they do not perform actual work. The electrical power input is converted into heat. It is therefore desirable to provide a way to recover a significant portion of the electrical energy used to operate computer logic circuitry and thereby reduce the power needs of the computer and, at the same time, the amount of heat generated.